Hybrid dedicated reference signal method and system

ABSTRACT

The transmission and decoding of resource blocks (RBs) transmitted via a multiple-input multiple-output (MIMO) antenna having a plurality of transmit antennas is disclosed. Each RB includes a plurality of resource elements (REs). Each RE is reserved for one of a common reference signal (CRS) associated with one of the transmit antennas, a dedicated reference signal (DRS) including a single beamformed or precoded pilot, a DRS including a composite beamformed or precoded pilot, and a data symbol. Each RB may include a “control type” data symbol that indicates a DRS mode associated with the RB. In one DRS mode, each DRS includes a single beamformed or precoded pilot. In another DRS mode, each DRS includes a composite beamformed or precoded pilot. In yet another DRS mode, single beamformed or precoded pilots, and composite beamformed or precoded pilots, may coexist and be transmitted simultaneously within the same RBs or in different RBs.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/052,842, filed Mar. 21, 2008, which claims the benefit of U.S.Provisional Patent Application Ser. No. 60/896,093 filed Mar. 21, 2007.Each of the above-referenced applications is incorporated by referenceherein.

FIELD OF INVENTION

This application is related to wireless communications.

BACKGROUND

Beamforming or precoding information needs to be communicated from atransmitter, (e.g., a base station), to receiver, (e.g., a wirelesstransmit/receive unit (WTRU)), to avoid a channel mismatch betweentransmitting and receiving signals. This is in particularly importantfor multiple-input multiple-output (MIMO) data demodulation whenbeamforming and precoding are used. When a receiver uses incorrectchannel responses for data detection, significant performancedegradation can occur.

Generally, beamforming or precoding information may be communicatedusing explicit control signaling, particularly when the transmitter andreceiver are restricted to the use of limited sets of antenna weightcoefficients for beamforming and precoding. The limited sets of antennaweight coefficients are sometimes referred to as a beamforming orprecoding codebook. Explicit signaling to communicate beamforming orprecoding information from a transmitter to a receiver may incur largesignaling overhead, particularly for a large size codebook. When thetransmitter and the receiver are not restricted to the use limited setsof antenna weight coefficients for beamforming and precoding, theexplicit signaling of beamforming or precoding information via a controlchannel is no longer possible. Since incorrect effective channelresponse information or precoding information results in significant biterror rate (BER) and/or block error rate (BLER) floors, efficientmethods for obtaining accurate effective channel response informationare desirable. Additionally, efficient schemes for achievingsatisfactory performance and overhead trade-off are desirable.

SUMMARY

The transmission and decoding of resource blocks (RBs) transmitted via aMIMO antenna having a plurality of transmit antennas is disclosed. EachRB includes a plurality of resource elements (REs). Each RE is reservedfor one of a common reference signal (CRS) associated with one of thetransmit antennas, a dedicated reference signal (DRS) including a singlebeamformed or precoded pilot, a DRS including a composite beamformed orprecoded pilot, and a data symbol. Each RB may include a “control type”data symbol that indicates a DRS mode associated with the RB. In one DRSmode, each DRS includes a single beamformed or precoded pilot. Inanother DRS mode, each DRS includes a composite beamformed or precodedpilot. In yet another DRS mode, single beamformed or precoded pilots,and composite beamformed or precoded pilots, may coexist and betransmitted simultaneously within the same RBs or in different RBs.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description of a preferred embodiment, given by way of exampleand to be understood in conjunction with the accompanying drawingswherein:

FIG. 1 shows a wireless communication system including a base stationand a WTRU;

FIGS. 2-8 show various examples of RB structures transmitted by the basestation in the system of FIG. 1;

FIG. 9 is a flow diagram of a procedure of generating an effectivechannel response estimate used by the WTRU in the system of FIG. 1 todetect/demodulate data in RB structures transmitted by the base stationin the system of FIG. 1;

FIG. 10 is a block diagram of the base station in the system of FIG. 1;

FIGS. 11 and 12 are block diagrams of the WTRU in the system of FIG. 1.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “base station” includes but isnot limited to a Node-B, a site controller, an access point (AP), or anyother type of interfacing device capable of operating in a wirelessenvironment.

FIG. 1 shows a wireless communication system 100 including a basestation 105 and a WTRU 110. The base station 105 may include a MIMOantenna 115 having a plurality of transmit antennas 115A, 115B, 115C and115D. The WTRU 110 may also include a MIMO antenna 120 having aplurality of receive antennas 120A, 120B, 120C and 120D. The basestation 105 communicates with the WTRU 110 by transmitting RBs 125 tothe WTRU 110. Each of the RBs 125 has a particular RB structure thatincludes a plurality of REs. In accordance with the particular RBstructure, each RE may be reserved for one of the following:

1) a common reference signal (CRS) associated with one of the transmitantennas 115A, 115B, 115C and 115D of the base station 105;

2) a DRS including a single beamformed or precoded pilot;

3) a DRS including a composite beamformed or precoded pilot; and

4) a data symbol.

At least a portion of data symbols reserved by REs of the RBs 125 are“control type” data symbols that include a DRS mode indicator. Oncedecoded, the DRS mode indicator enables the WTRU 110 to properlydetect/demodulate data symbols in the RBs 125 transmitted by the basestation 105.

Several ways of balancing between performance and overhead for obtainingeffective channel response information and/or beamforming or precodinginformation, (such as by PMI validation), may be utilized. A hybrid DRSscheme in which REs are reserved for DRSs including a single beamformedor precoded pilot and/or a composite beamformed or precoded pilot isintroduced, where a plurality (N) of DRSs per RB are used.

FIG. 2 shows an example of an RB structure that may be transmitted bythe base station 105. Each of a plurality of RBs 205 and 210 includes aplurality of REs reserved for data symbols (D), a plurality of REsreserved for CRSs associated with respective base station transmitantennas (T₁-T₄), and a plurality of REs reserved for DRSs (P), whichinclude either a single beamformed or precoded pilot, or a compositebeamformed or precoded pilot. As shown in FIG. 2, the DRSs are reservedby REs 215, 220, 225, 230, 235, 240, 245, 250, 255, 260, 265 and 270.

In one configuration or mode, (i.e., DRS mode 1), N DRSs include Nsingle beamformed pilots or precoded pilots. FIG. 3 shows an example ofan RB structure that may be transmitted by the base station 105 inaccordance with DRS mode 1, whereby each of a plurality of RBs 305 and310 includes a plurality of REs reserved for data symbols (D), aplurality of REs reserved for CRSs associated with respective basestation transmit antennas (T₁-T₄), and a plurality of REs reserved forDRSs which include either a single beamformed or precoded pilot P₁, or asingle beamformed or precoded pilot P₂. Each single beamformed orprecoded pilot has a plurality of elements, each of which is transmittedby a respective transmit antenna of a MIMO antenna of the base station105. As shown in FIG. 3, the DRSs are reserved by REs 315, 320, 325,330, 335, 340, 345, 350, 355, 360, 365 and 370.

When DRS mode 1 is used, the effective channel response may be directlyestimated by the WTRU 110 using the DRSs (P₁ and P₂). In addition, aneffective channel response estimate may also be computed using a commonchannel and a precoding matrix obtained by precoding matrix verificationvia a DRS. If there are a small number of active MIMO layers, (i.e., asmall number of data streams transmission, such as one or perhaps twodata streams transmission,) DRS mode 1 may be used. DRS mode 1 issuitable for low to medium data rate transmission, or to increase therange of signal reception coverage.

In another configuration or mode, (i.e., DRS mode 2), N DRSs include Ncomposite beamformed or precoded pilots. FIG. 4 shows an example of anRB structure that may be transmitted by the base station 105 inaccordance with DRS mode 2, whereby each of a plurality of RBs 405 and410 includes a plurality of REs reserved for data symbols (D), aplurality of REs reserved for CRSs associated with respective basestation transmit antennas (T₁-T₄), and a plurality of REs reserved forDRSs which include a composite beamformed or precoded pilot (P₁+P₂).Each composite beamformed or precoded pilot has a plurality of elements,each of which is transmitted by a respective transmit antenna of a MIMOantenna of the base station 105. As shown in FIG. 4, the DRSs arereserved by REs 415, 420, 425, 430, 435, 440, 445, 450, 455, 460, 465and 470. In this case the effective channel response may be computedusing a common channel and a precoding matrix obtained by precodingmatrix verification via a DRS.

FIG. 5 shows another RB structure that also may be transmitted by thebase station 105 in accordance with DRS mode 2, but having asubstantially lower DRS density than the RB structure of FIG. 4, wherebyan RB 505 only has two REs 515 and 520 that are reserved for DRSs whichinclude a composite beamformed or precoded pilot (P₁+P₂), and an RB 510only has two REs 525 and 530 that are reserved for DRSs which include acomposite beamformed or precoded pilot (P₁+P₂).

The WTRU 110 may directly estimate the effective channel response usingdedicated pilots. In addition, an effective channel response may also becomputed using a precoding matrix obtained by precoding matrix index(PMI) verification via single beamformed or precoded pilots. If thereare large number of active MIMO layers, such as two, or more than twodata transmission streams, DRS mode 2 may be used. Thus, DRS mode 2 issuitable for medium to high data rate transmission.

The WTRU 110 may compute an effective channel response by multiplyingcommon channel response estimates, obtained from common pilots or CRSs,with a precoding matrix obtained from the DRSs. A PMI verification isperformed on the DRSs. More than two DRSs per RB may also be used toimprove performance. However, an increased overhead cost may beincurred. Additionally, various other combinations of allocating singlebeamformed pilots or precoded pilots and/or composite beamformed orprecoded pilots to DRSs in the RBs are also possible.

In another configuration or mode, (i.e., DRS mode 3), single beamformedor precoded pilots, and composite beamformed or precoded pilots, maycoexist and be transmitted simultaneously within the same RBs or indifferent RBs. Thus, in accordance with DRS mode 3, the DRSs in aparticular RB may include one of the following:

1) only single beamformed or precoded pilots;

2) only composite beamformed or precoded pilots; and

3) a combination of single beamformed or precoded pilots, and compositebeamformed or precoded pilots.

FIG. 6 shows an example of an RB structure that may be transmitted bythe base station 105 in accordance with DRS mode 3, whereby a firstparticular RB 605 includes a plurality of REs 615, 620, 625, 630, 635and 640 that are reserved for DRSs that only include single beamformedor precoded pilots (P₁ and P₂), and a second particular RB 610 includesa plurality of REs 645, 650, 655, 660, 665 and 670 that are reserved forDRSs that only include composite beamformed or precoded pilots (P₁+P₂).

Single beamformed or precoded pilots are included only in the DRSs inthe first particular RB 605, whereby each DRS symbol carries one singlebeamformed or precoded pilot vector. Composite beamformed or precodedpilots are included only in the DRSs in the second particular RB 610.The composite beamformed or precoded pilots (P₁+P₂) may be generated byadding individual single beamformed or precoded pilots (P₁ and P₂)together. The single beamformed or precoded pilot vectors are added toone another, and the resulting composite beamformed or precoded pilot istransmitted in one or more DRS symbols. Thus, in the hybrid DRSconfiguration described above, some of the DRSs include singlebeamformed or precoded pilots across different RBs, and some of the DRSsinclude composite beamformed or precoded pilot across different RBs.

FIG. 7 shows another example of an RB structure that may be transmittedby the base station 105 in accordance with DRS mode 3. A firstparticular RB 705 in the RB structure of FIG. 7 includes a first groupof REs 715, 725, 730 and 740 that are reserved for DRSs that onlyinclude single beamformed or precoded pilots (P₁ and P₂), and a secondgroup of REs 720 and 735 that are reserved for DRSs that only includecomposite beamformed or precoded pilots (P₁+P₂). A second particular RB710 in the RB structure of FIG. 7 only includes REs 745, 750, 755, 760,765 and 770 that are reserved for DRSs that only include compositebeamformed or precoded pilots (P₁+P₂).

FIG. 8 shows yet another example of an RB structure that may betransmitted by the base station 105 in accordance with DRS mode 3. Afirst particular RB 805 in the RB structure of FIG. 8 includes a firstgroup of REs 815, 825, 830 and 840 that are reserved for DRSs that onlyinclude single beamformed or precoded pilots (P₁ and P₂), and a secondgroup of REs 820 and 835 that are reserved for DRSs that only includecomposite beamformed or precoded pilots (P₁+P₂). A second particular RB805 in the RB structure of FIG. 8 includes a third group of REs 845,855, 860 and 870 that are reserved for DRSs that only include singlebeamformed or precoded pilots (P₁ and P₂), and a fourth group of REs 850and 865 that are reserved for DRSs that only include compositebeamformed or precoded pilots (P₁+P₂). Each DRS symbol carries onesingle beamformed or precoded pilot vector, or one composite beamformedor precoded pilot vector.

Thus, FIG. 8 depicts a hybrid configuration whereby two thirds of theDRS REs in each RB 805 and 810 are single beamformed or precoded pilotsand one third of DRS REs in each RB 805 and 810 are composite beamformedor precoded pilots. Other RB structure configurations are also possibleby changing the ratio of DRS REs including single beamformed or precodedpilots to DRS REs including composite beamformed or precoded pilots inthe same RB.

Although the RB structures depicted by FIGS. 2-8 show that each of theRBs have 84 (12×7) REs, an RB structure of any dimension may be used.Furthermore, the RE positions of the data symbols (D), CRSs (T₁-T₄), andDRSs (P₁, P₂, and P₁+P₂) are presented as an example only, and any otherdesirable configuration of the RB structure may be used. Furthermore,although only two single beamformed or precoded pilots (P₁ and P₂) areshown as examples in FIGS. 3-8 for simplicity, there could generally bemore than two single beamformed or precoded pilots to support two ormore data transmission streams.

The use of a single beamformed or precoded pilot may avoid incorrectdetection of beamforming or precoding information, but comes at the costof increased overhead. The use of a composite beamformed or precodedpilot may reduce overhead, but at the cost of possible incorrectbeamforming or precoding information detection. A hybrid DRS scheme thatcombines single beamformed or precoded pilots and composite beamformedor precoded pilots can achieve an efficient trade-off betweenperformance and overhead.

In one example, if there are M MIMO transmission layers, which indicateM single beamformed or precoded pilot vectors (i.e., independent datastreams) that can be transmitted, denoted as P₁, P₂, P₃ and P_M, and NDRSs within an RB, the N DRSs are partitioned into two different groups:group 1 and group 2. Group 1 has N1 DRSs which transmit singlebeamformed or precoded pilot vectors. One DRS transmits one of the Msingle beamformed or precoded pilot vectors. FIGS. 2-8 depict variousexamples of RB block structures for which a DRS symbol transmits aparticular beamformed or precoded pilot vector. Group 2 has N2,(N2=N−N1), DRSs which transmit composite beamformed or precoded pilots.A composite pilot is a superposition or addition of two or more singlebeamformed or precoded pilot vectors. For example, a composite pilotP_c1 may be a superposition of P1 and P2, i.e., P_c1=P1+P2. Or acomposite pilot P_c2 may be a superposition of all pilot vectors suchthat P_c2=P1+P2+ . . . +P_M. A composite pilot P_c may be any propernumber of single beamformed or precoded pilot vectors, and anycombinations of them. For example, for a composite pilot (P_c1) with twosingle beamformed or precoded pilot vectors that are superpositioned,the composite pilot vector may be P1+P2, P1+P3, P1+P_M, P2+P1, and thelike.

Referring back to FIG. 1, if the system 100 is a two mode system capableof only operating in accordance with DRS mode 1 and DRS mode 2, the DRSmode indicators in the “control type” data symbols of the RBstransmitted by the base station 105 may indicate to the WTRU 110 whichone of the two modes the system 100 is currently operating in. For theDRS mode 1, the RBs transmitted by the base station 105 only includeDRSs including single beamformed or precoded pilots. For DRS mode 2, theRBs transmitted by the base station 105 only include DRSs includingcomposite beamformed or precoded pilots. A one bit DRS mode indicator in“control type” data symbols of the RBs may be used to instruct the WTRU110 to switch between DRS mode 1 and DRS mode 2.

It is also possible to have a DRS mode 0 in which there are no REsreserved for DRS. Referring back to FIG. 1, if the system 100 is a twomode system capable of only operating in accordance with DRS mode 0, (noREs reserved for DRS), and DRS mode 1, (REs reserved for DRSs includingsingle beamformed or precoded pilots), the DRS mode indicators in the“control type” data symbols of the RBs transmitted by the base station105 may indicate to the WTRU 110 which one of the two modes the system100 is currently operating in. For the DRS mode 1, the RBs transmittedby the base station 105 only include DRSs including single beamformed orprecoded pilots. For DRS mode 0, the RBs transmitted by the base station105 include no DRSs, and thus do not include single or compositebeamformed or precoded pilots. A one bit DRS mode indicator in “controltype” data symbols of the RBs may be used to instruct the WTRU 110 toswitch between DRS mode 1 and DRS mode 0. “Control type” data symbolsmay carry either higher layer signaling, (e.g., layer 2 (L2)/layer 3(L3) signaling), or lower layer signaling, (e.g., layer 1 (L1)signaling).

Still referring to FIG. 1, if the system 100 is a four mode systemcapable of operating in accordance with DRS mode 1, DRS mode 2, DRS mode3 and DRS mode 0, the DRS mode indicator, (having more than 1 bit), mayindicate which DRS mode and/or configuration the WTRU 110 should operatein.

DRS mode indicator signaling may be communicated via higher layersignaling, (e.g., L2/L3 signaling), using “bits” which are carried byREs reserved for data in the RBs. It is also possible to communicate DRSmode indicator signaling to users via lower layer signaling, (e.g., L1signaling).

A DRS mode 1 and mode 2 may be combined to create additional DRSoperation modes. DRS mode 3 may be defined in such way that the firsthalf of the DRSs are used for single beamformed or precoded pilottransmission and the second half of DRSs are used for compositebeamformed or precoded pilot transmission. Furthermore, depending on thepartitioning, (e.g., which and how many DRSs), and the layout of the DRStypes, (i.e., DRSs including a single beamformed or precoded pilot, andDRSs including a composite beamformed or precoded pilot), additional DRSmodes may be created. For systems using three or four modes, two bitsmay be used in the DRS indicator. For systems using more than fourmodes, Y bits may be used, where Y>2.

DRS mode 1 including single beamformed or precoded pilots is suitablefor non-codebook based beamforming or precoding. DRS mode 2 includingcomposite beamformed or precoded pilots is suitable for codebook basedbeamforming or precoding. DRS mode 3 including hybrid single andcomposite beamformed or precoded pilots is suitable for bothnon-codebook and codebook based beamforming or precoding coexisting inthe same system.

FIG. 9 is a flow diagram of a procedure 900, implemented in the system100 of FIG. 1, of generating an effective channel response estimate usedby the WTRU 110 to detect/demodulate data in RB structures transmittedby the base station 105. In step 905, the base station 105 transmits RBsto the WTRU 110 in accordance with a DRS mode determined based on, butnot limited to, a channel condition, WTRU speed and/or a data rate. Instep 910, the WTRU 110 receives the RBs, estimates either a common oreffective channel response, and decodes a DRS mode indicator located in“control type” data symbols in the RBs. The “control type” data symbolseither represent higher layer signaling (e.g., layer 2/3 signaling) orlower layer signaling, (e.g., layer 1 signaling). In step 915, the WTRU110 uses the DRS mode indicator to determine which REs in the RBs 125are reserved for DRSs, and for each particular DRS, the WTRU 110determines whether the particular DRS is a single beamformed or precodedpilot, or a composite beamformed or precoded pilot. In step 920, theWTRU 110 estimates an effective channel response based on thedeterminations of step 915. Finally, in step 925, the WTRU uses theeffective channel response estimate to performdetection/demodulation/decoding of data in the RBs 125 transmitted bythe base station 105.

The estimation of an effective channel response may be improved usingboth single beamformed or precoded pilots, and composite beamformed orprecoded pilots. The effective channel response may be obtained (eitherdirectly or indirectly) from single beamformed or precoded pilots. Theestimates of effective channel responses can be improved if both directand indirect estimates from single beamformed or precoded pilots arecombined. In the case when the effective channel response may also beobtained from composite beamformed or precoded pilots, the estimates ofeffective channel responses can be further improved if estimates fromboth single and composite beamformed or precoded pilots are combined.

In a two MIMO layer example, the effective channel response of each MIMOlayer is estimated using a beamformed or precoded pilot. H_eff_d isdenoted as the effective channel matrix obtained from direct estimation.The beamforming or precoding vector index (PVI) of each layer isobtained via PVI validation. The effective channel response of eachlayer is computed by multiplying a common channel response estimate witheach PVI. H_eff_c is denoted as the effective channel matrix obtainedfrom computation. H_eff_d and H_eff_c may then be averaged or combined,and weight coefficients may be applied to H_eff_d and H_eff_c whencombining such that H_eff=w1×H_eff_d+w2×H_eff_c where w1 and w2 arecombining weights.

FIG. 10 is a block diagram of a base station 1000 that is configured totransmit RBs, in accordance with a particular DRS mode. The base station1000 may include a MIMO antenna 1010, a receiver 1015, a processor 1020and a transmitter 1025. The MIMO antenna 1010 comprises a plurality oftransmit antennas. The processor 1020 determines whether the transmittershould transmit the RBs in accordance with DRS mode 0, DRS mode 1, DRSmode 2 or DRS mode 3, which is selected based on channel conditionsdetermined by the receiver 1015, the speed of a WTRU and/or a data rate.The processor 1020 generates RBs in accordance with the selected DRSmode, whereby the RBs include “control type” data symbols including atleast one DRS mode indicator bit. The RBs are transmitted by thetransmitter 1025 via the transmit antennas of the MIMO antenna 1010.

The transmitter 1025 may be configured to transmit a plurality of RBsvia the MIMO antenna 1010. Each RB comprises a plurality of REs. Each REmay be reserved for one of a CRS, a DRS including a single pilot, a DRSincluding a composite pilot, and a data symbol. The processor 1020 maybe configured to determine a particular RB structure for the RBs. EachRB may include at least one “control type” data symbol having at leastone DRS mode indicator bit which indicates the particular RB structure,as determined by the processor 1020.

The processor 1020 may be configured to switch from one particular RBstructure to another RB structure in response to detecting a change inat least one of a channel condition, a speed of a WTRU and a data rate.For example, the processor 1020 may be configured to switch thestructure of the RBs from a first configuration in which a subset of theplurality of REs in each RB is reserved for DRSs including singlebeamformed or precoded pilots, (i.e., DRS mode 1), to a secondconfiguration in which no REs are reserved for DRSs, (i.e., DRS mode 0).Alternatively, the processor 1020 may be configured to switch thestructure of the RBs from a first configuration in which no REs arereserved for DRSs, (i.e., DRS mode 0), to a second configuration inwhich a subset of the plurality of REs in each RB is reserved for DRSsincluding single beamformed or precoded pilots, (i.e., DRS mode 1).

FIG. 11 is a block diagram of a WTRU 1100 configured to receive the RBstransmitted by the base station 1000 of FIG. 10, anddetect/demodulate/decode data in the RBs based on a particular DRS modeindicated by the at least one DRS mode indicator bit. The WTRU 1100 mayinclude a MIMO antenna 1105, a fast Fourier transform (FFT) unit 1115, asignal parsing unit 1125, a channel estimation unit 1140 and a datadetection/demodulation/decoding unit 1150. The MIMO antenna 1105comprises a plurality of receive antennas, and the FFT unit 1115comprises a plurality of FFT subassemblies corresponding to respectiveones of the receive antennas of the MIMO antenna 1105. The MIMO antenna1105 receives RBs transmitted by the base station 1000 of FIG. 10 andforwards a corresponding time domain signal 1110 to the FFT unit 1115,which converts the time domain signal 1110 to a frequency domain signal1120. The signal parsing unit 1125 parses the frequency domain signal1120 into the DRSs/CRSs 1130 of the RBs and data (D) 1135 of the RBs.The signal parsing unit 1125 forwards the DRSs/CRSs 1130 to the channelestimation unit 1140, and forwards the data (D) 1140 to the datadetection/demodulation/decoding unit 1150, which decodes “control type”data symbols in the data (D) that includes at least one DRS modeindicator bit.

The signal parsing unit 1125 parses the frequency domain signal 1120based on a decoded DRS mode indicator signal 1160 generated by the datadetection/demodulation/decoding unit 1150. The WTRU 1100 receiver andits signal parsing unit 1125 are configured in accordance with aparticular DRS mode indicated by the decoded DRS mode indicator signal1160. The decoded DRS mode indicator signal 1160 instructs the WTRU 1100receiver and the signal parsing unit 1125 to forward the DRSs/CRSs 1130to the channel estimation unit 1140, and to forward the data (D) 1140 tothe data detection/demodulation/decoding unit 1150 based on the RBstructure, (i.e., DRSs/CRSs/Ds layout), indicated by the decoded DRSmode.

If “control type” data symbols are sent via lower layer signaling,(e.g., L1 signaling), the channel estimation unit 1140 estimates thecommon channel response based on the CRSs and forwards common channelresponse estimation information 1145 to the datadetection/demodulation/decoding unit 1150, which decodes the “controltype” data (D) 1135 that contains the DRS mode indicator based on thecommon channel response estimation information 1145. Based on thedecoded DRS mode indicator, the signal parsing unit 1125 forwards theDRSs/CRSs 1130 to the channel estimation unit 1140, and forwards thedata (D) 1140 to the data detection/demodulation/decoding unit 1150. Thechannel estimation unit 1140 estimates the effective channel responsebased on the DRSs and forwards common channel response estimationinformation 1145 to the data detection/demodulation/decoding unit 1150,which decodes the “data type” data (D) 1135 based on the common channelresponse estimation information 1145.

If “control type” data symbols are sent via higher layer signaling,(e.g., L2/3 signaling), the channel estimation unit 1140 estimates thecommon and/or effective channel response, (depending on the current DRSmode), based on the CRSs and/or DRSs and forwards effective channelresponse estimation information 1145 to the datadetection/demodulation/decoding unit 1150, which decodes the “controltype” data (D) 1135 that contains a DRS mode indicator based on theeffective channel response estimation information 1145. The decoded DRSindicator is used to configure and switch the DRS mode of the WTRU 1100,which will be used for subsequent transmission and receiving. Forcurrent transmission, the WTRU 1100 uses the decoded DRS mode indicatorin the previous transmission and receiving.

FIG. 12 is a block diagram of another WTRU 1200 configured to receivethe RBs transmitted by the base station 1000 of FIG. 10, anddetect/demodulate/decode data in the RBs based on a particular DRS modeindicated by the at least one DRS mode indicator bit. The WTRU 1200 mayinclude a MIMO antenna 1205, a fast Fourier transform (FFT) unit 1215, asignal parsing unit 1225, a beamforming or precoding matrix index (PMI)validation unit 1245, a channel estimation unit 1255, an effectivechannel matrix unit 1265, and a data detection/demodulation/decodingunit 1275. The MIMO antenna 1205 comprises a plurality of receiveantennas, and the FFT unit 1215 comprises a plurality of FFTsubassemblies corresponding to respective ones of the receive antennasof the MIMO antenna 1205. The MIMO antenna 1205 receives RBs transmittedby the base station 1000 of FIG. 10 and forwards a corresponding timedomain signal 1210 to the FFT unit 1215, which converts the time domainsignal 1210 to a frequency domain signal 1220. If the DRS mode indicatoris sent via higher layer signaling, (e.g., L2/3 signaling), the WTRU1200 is configured and switched to the DRS mode based on the previousreceived and decoded DRS mode indicator. The signal parsing unit 1225parses the frequency domain signal 1220 into the DRSs 1230, the CRSs1235 and data (D) 1240 of the RBs. The signal parsing unit 1225 forwardsthe DRSs 1230 to the PMI validation unit 1245, forwards the CRSs 1235 tothe channel estimation unit 1255, and forwards the data (D) 1240 to thedata detection/demodulation/decoding unit 1275, which decodes datasymbols in the data (D). The data detection/demodulation/decoding unit1275 will decode “control type” data symbols in the data (D) thatcontains at least one DRS mode indicator bit, if the DRS mode indicatoris sent via lower layer signaling (e.g., L1 signaling). The beamformingor PMI validation unit 1245 forwards a PMI validation signal 1250 to theeffective channel matrix unit 1265. The channel estimation unit 1255estimates the common channel response based on the CRSs 1235 andforwards common channel response estimation information 1260 to theeffective channel matrix unit 1265, which generates an effective channelmatrix information signal 1270. The effective channel matrix unit 1265forwards the effective channel matrix information signal 1270 to thedata detection/demodulation/decoding unit 1275, which decodes the data(D) 1240 based on the effective channel matrix information signal 1270to generate decoded data 1280.

The signal parsing unit 1225 parses the frequency domain signal 1220based on a decoded DRS mode indicator signal 1285 generated by the datadetection/demodulation/decoding unit 1275. The WTRU 1200 receiver andits signal parsing unit 1225 are configured in accordance with aparticular DRS mode indicated by the decoded DRS mode indicator signal1285. The decoded DRS mode indicator signal 1285 instructs the WTRU 1200receiver and the signal parsing unit 1225 to forward the CRSs 1235 tothe channel estimation unit 1255, to forward the DRSs 1230 to the PMIvalidation unit 1245, and to forward the data (D) 1240 to the datadetection/demodulation/decoding unit 1275 based on the RB structure,(i.e., DRSs/CRSs/Ds layout), indicated by the decoded DRS mode indicatorsignal 1285.

The PMI validation unit 1245 performs blind detection for thebeamforming or precoding information that is used at the base station1000. The algorithm for such a blind detection searches through abeamforming or precoding codebook for the best beamforming or precodinginformation based on a certain criteria, such as “minimum distance” ofsignal or “maximum likelihood” of detection (see Equations (5) and (6)).

In the beamformed or precoded pilot method, each dedicated pilot (P_m)transmits one beamformed or precoded pilot via all antennas. Forexample, if there are four antennas having two data streams each, adedicated pilot m=1, 2 transmits the following precoded pilot:

${P_{m} = {\begin{bmatrix}v_{m\; 1} \\v_{m\; 2} \\v_{m\; 3} \\v_{m\; 4}\end{bmatrix} \cdot C_{m}}},$where [v_m1, . . . , v_m4]^T is the precoding vector of the m-th streamand C_m is a pilot code or sequence. For M data streams, M dedicatedpilots are required and M precoded pilots are transmitted by M dedicatedpilots, each in different subcarriers.

The channel is estimated via each dedicated pilot across all antennas.For example, if there are four antennas and two streams, the receivedsignal model for each dedicated pilot m=1, 2 is:

$\begin{matrix}{{\overset{\rightarrow}{y}}_{m} = {{{\begin{bmatrix}h_{11} & h_{12} & h_{13} & h_{14} \\h_{21} & h_{22} & h_{23} & h_{24}\end{bmatrix}\begin{bmatrix}v_{m\; 1} \\v_{m\; 2} \\v_{m\; 3} \\v_{m\; 4}\end{bmatrix}} \cdot C_{m}} + {\overset{\rightarrow}{n}.}}} & {{Equation}\mspace{14mu}(1)}\end{matrix}$The effective channel matrix is:

$\begin{matrix}{H_{eff} = {\begin{bmatrix}h_{{eff},11} & h_{{eff},12} \\h_{{eff},21} & h_{{eff},22}\end{bmatrix}.}} & {{Equation}\mspace{14mu}(2)}\end{matrix}$

The effective channel response can be estimated using two dedicatedpilots as an example as follows:

$\begin{matrix}{{{\overset{\rightarrow}{y}}_{1} = {{\begin{bmatrix}h_{{eff},11} \\h_{{eff},21}\end{bmatrix}.C_{1}} + \overset{\rightarrow}{n}}};{and}} & {{Equation}\mspace{14mu}(3)} \\{{\overset{\rightarrow}{y}}_{2} = {{\begin{bmatrix}h_{{eff},12} \\h_{{eff},22}\end{bmatrix}.C_{2}} + {\overset{\rightarrow}{n}.}}} & {{Equation}\mspace{14mu}(4)}\end{matrix}$The effective channel responses may be estimated using both common anddedicated pilots. Channel H may be obtained from a common pilot, T_m.The effective channel responses may be computed using multiplication ofH and V, i.e., H_eff=HV, where V is the beamforming or precoding vectoror matrix. The effective channel response H_eff may be obtained fromdedicated pilot P_m (=V*C_m) by performing channel estimation algorithmfor Equations (3) and (4).

When decoding the beamforming or precoding matrices/vectors, beamformingor precoding vectors can be detected using the following algorithms foreach of the M beamformed or precoded pilots, m=1, 2, . . . M:

$\begin{matrix}{{\hat{V}}_{m} = {\arg\limits_{V_{i}}\min{{{y_{m} - {H_{m}V_{i}C_{m}}}}.}}} & {{Equation}\mspace{14mu}(5)}\end{matrix}$Once the beamforming or precoding matrix or vector is obtained, theeffective channel response can be computed by H_eff=H×V_hat where H iscommon channel response and V_hat is the detected beamforming orprecoding matrix or vector. The effective channel response may also beestimated above for each of the M beamformed or precoded pilots, m=1, 2,. . . M.

A beamforming or precoding matrix or vectors may be detected using thefollowing algorithms for M beamformed or precoded pilots:

$\begin{matrix}{{\hat{V} = {\arg\limits_{V_{i}}\;{\min\left( {\sum\limits_{m = 1}^{M}{{y_{m} - {H_{m}V_{i}C_{m}}}}} \right)}}},} & {{Equation}\mspace{14mu}(6)}\end{matrix}$where V_hat is the detected beamforming or precoding matrix or vectors.

The effective channel response H_eff may be obtained from compositebeamformed or precoded pilots or composite dedicated pilot. Thebeamforming or precoding matrices or vectors can be detected using Mcomposite beamformed or precoded pilots:

$\begin{matrix}{{\hat{V} = {\arg\limits_{\{ V_{i}\}}{\min\left( {\sum\limits_{m = 1}^{M}{{y_{m} - {\sum\limits_{V_{i} \in {\{ V_{i}\}}}^{\;}{H_{m}V_{i}C_{m}}}}}} \right)}}},} & {{Equation}\mspace{14mu}(7)}\end{matrix}$where {Vi} is a set of V. For example {Vi} can be {V1, V2} or {V1, V3}or {V1, V2, V3}, {V1, V2, V3, V4}, and the like.

Combining the estimates of effective channel responses from both commonand dedicated pilots or composite dedicated pilots, the performance ofchannel response estimation and data detection may be improved.Alternatively, one may reduce the number of deployed dedicated pilots orcomposite dedicated pilots for the same performance.

Examples of one MIMO layer, two MIMO layer, and three or more MIMOlayers are as follows:

One layer:

-   -   1) Obtain H_eff_d→ Use H_eff_d. (see Equations (3) and (4).)        Subscript d means H_eff can be obtained by direct estimation.        Same for the following.

or

-   -   2) Detect PVI→ compute and use H_eff_c. (obtained from        Equations (5) and (6).) Subscript c means H_eff is obtained by        computation. The same applies for the following.

or

-   -   3) Obtain H_eff_d, detect PVI and compute H_eff_c. Average or        combine H_eff_d and H_eff_c.

Two MIMO layers:

-   -   1) Obtain h_eff_d1 and h_eff_d2, H_eff_d=[h_eff_d1 h_eff_d2].    -   2) Obtain PVI1, PVI2→ compute h_eff_c1 and h_eff_c2,        H_eff_c=[h_eff_c1 h_eff_c2].    -   3) Average or combine H_eff_d and H_eff_c.

Three or more MIMO layers:

-   -   1) Obtain PMI→ compute H_eff_c.

Although features and elements are described above in particularcombinations, each feature or element can be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB)module.

What is claimed is:
 1. A wireless communication method of transmittingresource blocks (RBs), the method comprising: generating multiple RBs,wherein: each RB of the multiple RBs comprises multiple resourceelements (REs); the REs comprise at least one dedicated reference signal(DRS) specific to a single wireless transmit/receive unit (WTRU) and atleast one control-type data symbol; the at least one control-type datasymbol comprises a DRS mode indicator signaling any of multiple DRSmodes; in a first DRS mode of the multiple DRS modes, a firstconfiguration of the REs is used for the at least one DRS and the atleast one DRS comprises a respective at least one single beamformed orprecoded pilot; and in a second DRS mode of the multiple DRS modes, asecond configuration of the REs is used for the at least one DRS and theat least one DRS comprises a respective at least one compositebeamformed or precoded pilot; and transmitting the RBs via amultiple-input multiple-output (MIMO) antenna.
 2. The method of claim 1,wherein each DRS mode of the multiple DRS modes is indicative of anumber of transmission layers.
 3. The method of claim 1, wherein one ormore RBs of the multiple RBs comprises the at least one control-typedata symbol that includes the DRS mode indicator.
 4. The method of claim1, wherein in a third DRS mode of the multiple DRS modes: a thirdconfiguration of the REs is used for the at least one DRS; the at leastone DRS of a first RB of the multiple RBs includes a respective at leastone single beamformed or precoded pilot; and the at least one DRS of asecond RB of the multiple RBs include a respective at least onecomposite beamformed or precoded pilot.
 5. The method of claim 1,wherein in a third DRS mode of the multiple DRS modes: a thirdconfiguration of the REs is used for the at least one DRS; the at leastone DRS of a first RB of the multiple RBs includes a respective at leastone single beamformed or precoded pilot; the at least one DRS of asecond RB of the multiple RBs includes a respective at least onecomposite beamformed or precoded pilot; and the REs of a third RB of themultiple RBs lack DRSs.
 6. The method of claim 1, wherein in a third DRSmode of the multiple DRS modes: a third configuration of the REs is usedfor the at least one DRS; a first group of the REs is reserved for theat least one DRS formed as a single beamformed or precoded pilot; and asecond group of the REs is reserved for the at least one DRS formed as acomposite beamformed or precoded pilot.
 7. The method of claim 1,wherein in a third DRS mode of the multiple DRS modes: a thirdconfiguration of the REs is used for the at least one DRS; and the atleast one DRS comprises a respective at least one combination of asingle beamformed or precoded pilot and a composite beamformed orprecoded pilot.
 8. The method of claim 1, wherein in a third DRS mode ofthe multiple DRS modes: the at least one DRS is multiple DRSs; and theDRSs comprise at least one single beamformed or precoded pilot and atleast one composite beamformed or precoded pilot.
 9. The method of claim1, wherein the DRS mode indicator indicates a change in DRS mode.
 10. Abase station comprising: a multiple-input multiple-output (MIMO)antenna; a processor for generating multiple resource blocks (RBs),wherein: each RB of the multiple RBs comprises multiple resourceelements (REs); the REs comprise at least one dedicated reference signal(DRS) specific to a single wireless transmit/receive unit (WTRU) and atleast one control-type data symbol; the at least one control-type datasymbol comprises a DRS mode indicator signaling any of multiple DRSmodes; in a first DRS mode of the multiple DRS modes, a firstconfiguration of REs is used for the at least one DRS and the at leastone DRS comprises a respective at least one single beamformed orprecoded pilot; and in a second DRS mode of the multiple DRS modes, asecond configuration of the REs is used for the at least one DRS and theat least one DRS comprises a respective at least one compositebeamformed or precoded pilot; and a transmitter for transmitting thegenerated RBs via the MIMO antenna.
 11. The base station of claim 10,wherein each DRS mode of the multiple DRS modes is indicative of anumber of transmission layers.
 12. The base station of claim 10, whereinone or more RBs of the multiple RBs comprises the at least onecontrol-type data symbol that includes the DRS mode indicator.
 13. Thebase station of claim 10, wherein in a third DRS mode of the multipleDRS modes: a third configuration of the REs used for the at least oneDRS; the at least one DRS of a first RB of the multiple RBs includes arespective at least one single beamformed or precoded pilot; and the atleast one DRS of a second RB of the multiple RBs includes a respectiveat least one composite beamformed or precoded pilot.
 14. The WTRU ofclaim 10, wherein in a third DRS mode of the multiple DRS modes: a thirdconfiguration of the REs is used for the at least one DRS; the least oneDRS of a first RB of the multiple RBs includes a respective singlebeamformed or precoded pilot; the at least one DRS of a second RB of themultiple RBs includes a respective at least one composite beamformed orprecoded pilot; and the REs of a third RB of the multiple RBs lack DRSs.15. The base station of claim 10, wherein in a third DRS mode of themultiple DRS modes: a third configuration of the REs is used for the atleast one DRS; a first group of the REs is reserved for the at least oneDRS formed as a single beamformed or precoded pilot; and a second groupof the REs is reserved for the at least one DRS formed as a compositebeamformed or precoded pilot.
 16. The base station of claim 10, whereinin a third DRS mode of the multiple DRS modes: a third configuration ofthe REs is used for multiple DRSs; and the DRSs comprise a respective atleast one combination of a single beamformed or precoded pilot and acomposite beamformed or precoded pilot.
 17. The base station of claim10, wherein in a third DRS mode of the multiple DRS modes: the at leastone DRS is multiple DRSs; and the DRSs comprise at least one singlebeamformed or precoded pilot and at least one composite beamformed orprecoded pilot.
 18. The base station of claim 10, wherein the DRS modeindicator indicates a change in DRS mode.
 19. A base station comprising:a processor, transmitter and a multiple-input multiple output (MIMO)antenna, wherein: the transmitter is configured to transmit multipleresource blocks (RBs) via the MIMO antenna; each RB of the multiple RBscomprises multiple resource elements (REs); the REs comprise at leastone dedicated reference signal (DRS) specific to a single wirelesstransmit/receive unit (WTRU) and at least one control-type data symbol;the at least one control-type data symbol comprises a DRS mode indicatorsignaling any of a plurality of DRS modes; in a first DRS mode of themultiple DRS modes, a first configuration of REs is used for the atleast one DRS and the at least one DRS comprises a respective at leastone single beamformed or precoded pilot; and in a second DRS mode of themultiple DRS modes, a second configuration of the REs is used for the atleast one DRS and the at least one DRS comprises a respective at leastone composite beamformed or precoded pilot.
 20. The base station ofclaim 19, wherein one or more RBs of the multiple RBs comprise the atleast one control-type data symbol that includes the DRS mode indicator.21. The method of claim 1, wherein the REs comprise a common referencesignal (CRS) for a plurality of WTRUs.
 22. The method of claim 1,wherein the REs comprise a data symbol.
 23. The base station of claim10, wherein the REs comprise a common reference signal (CRS) for aplurality of WTRUs.
 24. The base station of claim 10, wherein the REscomprise a data symbol.
 25. The base station of claim 19, wherein theREs comprise a common reference signal (CRS) for a plurality of WTRUs.26. The base station of claim 19, wherein the REs comprise a datasymbol.